Figure 1.

Confocal images of the lower one-half of a spherical polystyrene bead containing a fluorescent dye in the outer layer. Image a is distorted in the z-plane by differences in refractive index among mounting materials. In image b, the pixel spacing in the z-plane has been corrected to make the image of the bead spherical (see text for discussion). The distances R (= 10.36 μ m) and r (= 7.25 μ m) represent the uncorrected and corrected radii, respectively. The image of the top one-half of the bead was further distorted by the light passing through the bead itself, and this portion of the image has been cropped for clarity.